The oysters we are slurping down are so fresh, we shouldn't be amazed to hear they were plucked from France's Bay of Arcachon only hours ago. But it comes as a surprise, because instead of eating them in a French brasserie, we are miles away on a beach lapped by a turquoise sea.

And although the oysters got here quicker than they would take to hit a Parisian supermarket shelf, it is not just the distance that makes me gulp with awe - it's the fact that we are in the Caribbean, that least gastronomic of destinations which hitherto had only battered my tastebuds with its various interpretations of jerk chicken.

We are in St Barthélemy, commonly known as St Barts, which might share the same sunshine with the rest of the Caribbean, but categorically does not eat off the same menu. The tiny island of just eight square miles is a French enclave in the tropics, which means it is par for the course to start off with croissants and pains au chocolat, head off for a day on the beach - interrupted by a lazy, luscious lunch on the sand - and finish with a gourmet extravaganza. And you get to pay for all of it in euros - quite a lot of euros.

St Barts is chic but not cheap, a fact that hits home in the capital Gustavia with its strip of shops like a baby Champs Elysées boasting names from Hermès to Cartier. Since David Rockefeller bought a place on the island in the 1950s, a long line of the rich and famous have flocked here, most recently Brad Pitt (famously snapped in the nude at the Toiny hotel), Tom Hanks and Halle Berry.

Beyond the glitz in Gustavia, though, you can see that the place has its roots in a foodie culture, with a French boulangerie by the post office and a seemingly endless variety of restaurants which go on to stretch around the island.

There is certainly choice in the number of eateries - 80 at the last count - but at the start of a week in the sun, we wondered how much choice there would be in the dishes. With no natural source of water, nothing is home-grown on St Barts and pretty much the only locally produced food is the fish. How many different ways can you serve bream, Mahi Mahi, and red snapper? The answer is quite a lot.

First, there is the carpaccio, thin slices of raw fish with lime and sometimes basil. There are fish casseroles bursting with flavour from the sea, dressings of mango, truffles and lemongrass - certainly nothing as banal as a simple grilled fish. To boost the variety, others types of fish are imported as well as shellfish, foie gras, duck and lamb from France, beef and lobster from the US and vegetables from neighbouring islands. There is also a strong Asian influence.

Add to the mixture a handful of top chefs and you have got the makings of months of mouth-watering meals that will have you clambering out of the sea at lunchtime to enjoy a feast of Michelin-star quality before returning to the beach. There is traditional French food, but it comes with a twist that might be as simple as the tomato and mango salad we tasted at Maya's, or as complicated as the scallops and truffle with cauliflower mousse accompanied by a mushroom and licorice soup at the Toiny.

'In the last eight years there has been a real evolution in the gastronomy here because we could get more produce direct from suppliers,' says Maxime Deschamps, chef at the Toiny. 'Holidaymakers used to just want chips. Now they know about truffles and that is what they want.'

You can't pass on the puddings either, especially if you're fond of moelleux au chocolat, that delicious half-cooked chocoholics' dream. There are lots of variations on ice cream and mousse, including a two-chocolate mousse with green tea ice cream, a frozen mint one, and the lightest vanilla ice cream layered with strawberries and lemongrass infusion.

Though your bank balance will take a bashing, if you take your food seriously, it's worth making St Barts part of your personal world gastro-tour. Don't just take it from me - my French boyfriend, François, who takes his food seriously, was raving over the meals, all served up in a glorious setting.

When you just want a night in, St Barts is more dial-a-chef than dial-a-pizza. We booked Jerome, a chef at the Terraza restaurant, who showed up at our villa to cook, serve and clean up while we sat in bliss, appreciating the light sea breeze and the balmy night air as we dined in a private heaven.

Nothing is ordinary in St Barts - even the welcome basket of food in our villa was gourmet. Expecting the useful things - bread, milk, eggs - I threw the fridge door open to carefully prepared pasta salad, roast chicken and cheese.

'You can't eat badly here,' says Philippe Masseglia, the chef at the Bartolomeo, at the Guanahani hotel. 'There is nothing but beach and food - no waterfalls to see and no ruins. Just good food.' He is almost right - in a week of solid eating in the name of research, we do have one meal that is not up to scratch.

It is at Nikki Beach, a club where medallion men with partners wearing fashion-label bikinis flip through Hello! magazine to see what those more famous than they are up to. I found the chicken tough, the salad tasteless and the service snooty, but as the club is frequented by It girls more concerned with spraying each other with bottles of champagne than eating, and whose waistlines only allow them to pick at their food, I don't suppose it's a problem.

We spend the short hours between meals exploring the corners of St Barts, driving around the rollercoaster roads that skirt the island, sometimes leaving nothing between us and the sea. You never know what is round the next bend; sometimes great views pop up from nowhere, the lush hillsides tumbling down into a sea of turquoise, other times it's a kamikaze local driver who has inherited his motoring skills from the French.

Making its daily rounds, we found the post van was typically French - La Poste emblazoned on its yellow side, a stunning contrast to the brilliant blue sea beyond. There is as much variety in the beaches of St Barts as there is in the restaurants, from the Shell Beach - the best spot to watch the sunset - to Governor's Beach, with its wide strip of golden sand backed by hills. The place to see and be seen, the beach at St Jean, is at the end of the island's small airstrip: the lack of safety barriers makes walking along the beach almost hazardous as small planes skim back and forth.

Just behind the beach strip is Chez Andy, an English-run restaurant. The simple pizza and salad bar is advertised with a sign that promises 'corked wine, warm beer, lousy food and a view of the car park'. It's effective advertising - the restaurant is packed, many of the bums on the seats belonging to discerning locals.

After a week of eating our way around the island, putting on a few pounds along the way, it is time to head home. As we pack our bags, the thought of airline food after a week's gastronomic indulgence is too much. Dashing into the deli Maya's to Go, opposite the airport, we shell out €50 for a gourmet picnic. It is worth it; when our fellow passengers are shuffling their forks around their unappetising airline fare, we are munching happily on ceviche and artichoke salad - a final taste of St Barts to make the memory linger a little longer on our lips.